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Schema-Representation

Doctrine has a very powerful abstraction of database schemas. It offers an object-oriented representation of a database schema with support for all the details of Tables, Sequences, Indexes and Foreign Keys. These Schema instances generate a representation that is equal for all the supported platforms. Internally this functionality is used by the ORM Schema Tool to offer you create, drop and update database schema methods from your Doctrine ORM Metadata model. Up to very specific functionality of your database system this allows you to generate SQL code that makes your Domain model work.

You will be pleased to hear, that Schema representation is completely decoupled from the Doctrine ORM though, that is you can also use it in any other project to implement database migrations or for SQL schema generation for any metadata model that your application has. You can easily generate a Schema, as a simple example shows:

1<?php
$schema = new \Doctrine\DBAL\Schema\Schema();
$myTable = $schema->createTable("my_table");
$myTable->addColumn("id", "integer", array("unsigned" => true));
$myTable->addColumn("username", "string", array("length" => 32));
$myTable->setPrimaryKey(array("id"));
$myTable->addUniqueIndex(array("username"));
$myTable->setComment('Some comment');
$schema->createSequence("my_table_seq");

$myForeign = $schema->createTable("my_foreign");
$myForeign->addColumn("id", "integer");
$myForeign->addColumn("user_id", "integer");
$myForeign->addForeignKeyConstraint($myTable, array("user_id"), array("id"), array("onUpdate" => "CASCADE"));

$queries = $schema->toSql($myPlatform); // get queries to create this schema.
$dropSchema = $schema->toDropSql($myPlatform); // get queries to safely delete this schema.


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Now if you want to compare this schema with another schema, you can use the Comparator class to get instances of SchemaDiff, TableDiff and ColumnDiff, as well as information about other foreign key, sequence and index changes.

1<?php
$comparator = new \Doctrine\DBAL\Schema\Comparator();
$schemaDiff = $comparator->compare($fromSchema, $toSchema);

$queries = $schemaDiff->toSql($myPlatform); // queries to get from one to another schema.
$saveQueries = $schemaDiff->toSaveSql($myPlatform);


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The Save Diff mode is a specific mode that prevents the deletion of tables and sequences that might occur when making a diff of your schema. This is often necessary when your target schema is not complete but only describes a subset of your application.

All methods that generate SQL queries for you make much effort to get the order of generation correct, so that no problems will ever occur with missing links of foreign keys.

Schema Assets

A schema asset is considered any abstract atomic unit in a database such as schemas, tables, indexes, but also sequences, columns and even identifiers. The following chapter gives an overview of all available Doctrine 2 schema assets with short explanations on their context and usage. All schema assets reside in the Doctrine\DBAL\Schema namespace.

This chapter is far from being completely documented.

Column

Represents a table column in the database schema. A column consists of a name, a type, portable options, commonly supported options and vendors specific options.

Portable options

The following options are considered to be fully portable across all database platforms:

  • notnull (boolean): Whether the column is nullable or not. Defaults to true.
  • default (integer|string): The default value of the column if no value was specified. Defaults to null.
  • autoincrement (boolean): Whether this column should use an autoincremented value if no value was specified. Only applies to Doctrine's smallint, integer and bigint types. Defaults to false.
  • length (integer): The maximum length of the column. Only applies to Doctrine's string and binary types. Defaults to null and is evaluated to 255 in the platform.
  • fixed (boolean): Whether a string or binary Doctrine type column has a fixed length. Defaults to false.
  • precision (integer): The precision of a Doctrine decimal or float type column that determines the overall maximum number of digits to be stored (including scale). Defaults to 10.
  • scale (integer): The exact number of decimal digits to be stored in a Doctrine decimal or float type column. Defaults to 0.

  • customSchemaOptions (array): Additional options for the column that are supported by all vendors:

    • unique (boolean): Whether to automatically add a unique constraint for the column. Defaults to false.

Common options

The following options are not completely portable but are supported by most of the vendors:

  • unsigned (boolean): Whether a smallint, integer or bigint Doctrine type column should allow unsigned values only. Supported only by MySQL. Defaults to false.
  • comment (integer|string): The column comment. Supported by MySQL, PostgreSQL, Oracle and SQL Server. Defaults to null.

Vendor specific options

The following options are completely vendor specific and absolutely not portable:

  • columnDefinition: The custom column declaration SQL snippet to use instead of the generated SQL by Doctrine. Defaults to null. This can useful to add vendor specific declaration information that is not evaluated by Doctrine (such as the ZEROFILL attribute on MySQL).

  • customSchemaOptions (array): Additional options for the column that are supported by some vendors but not portable:

    • charset (string): The character set to use for the column. Currently only supported on MySQL.
    • collation (string): The collation to use for the column. Supported by MySQL, PostgreSQL, Sqlite and SQL Server.
    • check (string): The check constraint clause to add to the column. Defaults to null.